Fix exact count that caused the RO replicate to fall over...

go.mod

@@ -1,6 +1,6 @@
 module heckel.io/ntfy/v2
 
-go 1.26.0
+go 1.25.8
 
 require (
 	cloud.google.com/go/firestore v1.25.0 // indirect
@@ -16,7 +16,7 @@ require (
 	github.com/urfave/cli/v2 v2.27.7
 	golang.org/x/crypto v0.55.0
 	golang.org/x/oauth2 v0.36.0 // indirect
-	golang.org/x/sync v0.23.0
+	golang.org/x/sync v0.22.0
 	golang.org/x/term v0.45.0
 	golang.org/x/time v0.15.0
 	google.golang.org/api v0.294.0

go.sum

@@ -221,8 +221,8 @@ golang.org/x/sync v0.3.0/go.mod h1:FU7BRWz2tNW+3quACPkgCx/L+uEAv1htQ0V83Z9Rj+Y=
 golang.org/x/sync v0.6.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sync v0.10.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
-golang.org/x/sync v0.23.0 h1:KameEIfc1IkluZyXWLn39Wd4tURc6GbCiISGiZm2bQk=
-golang.org/x/sync v0.23.0/go.mod h1:sUUOizhqBxiL6pEWpqNLUiaJn1ShEbZ6BBqskPbjZm0=
+golang.org/x/sync v0.22.0 h1:SZjpbeLmrCk4xhRSZFNZW5gFUeCeFgjekvI/+gfScek=
+golang.org/x/sync v0.22.0/go.mod h1:9xrNwdLfx4jkKbNva9FpL6vEN7evnE43NNNJQ2LF3+0=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

message/cache.go

@@ -300,7 +300,8 @@ func (c *Cache) MarkPublished(m *model.Message) error {
 	return err
 }
 
-// MessagesCount returns the total number of messages in the cache
+// MessagesCount returns the total number of messages in the cache. On Postgres, this is the
+// planner's estimate once the table has been analyzed, not an exact count.
 func (c *Cache) MessagesCount() (int, error) {
 	rows, err := c.db.ReadOnly().Query(c.queries.selectMessagesCount)
 	if err != nil {

message/cache_postgres.go

@@ -62,8 +62,13 @@ const (
 		ORDER BY time, id
 	`
 	postgresUpdateMessagePublishedQuery = `UPDATE message SET published = TRUE WHERE mid = $1`
-	postgresSelectMessagesCountQuery    = `SELECT COUNT(*) FROM message`
-	postgresSelectTopicsQuery           = `SELECT topic FROM message GROUP BY topic`
+	// Planner estimate, since a COUNT(*) scans the whole table; reltuples is -1 if never analyzed
+	postgresSelectMessagesCountQuery = `
+		SELECT CASE WHEN reltuples < 0 THEN (SELECT COUNT(*) FROM message) ELSE reltuples::BIGINT END
+		FROM pg_class
+		WHERE oid = 'message'::regclass
+	`
+	postgresSelectTopicsQuery = `SELECT topic FROM message GROUP BY topic`
 
 	postgresDeleteExpiredMessagesQuery         = `DELETE FROM message WHERE mid IN (SELECT mid FROM message WHERE expires <= $1 AND published = TRUE LIMIT $2)`
 	postgresMarkExpiredAttachmentsDeletedQuery = `UPDATE message SET attachment_deleted = TRUE WHERE mid IN (SELECT mid FROM message WHERE attachment_expires > 0 AND attachment_expires <= $1 AND attachment_deleted = FALSE LIMIT $2)`

message/cache_postgres_test.go

@@ -74,3 +74,28 @@ func TestPostgresStore_Migration_From14(t *testing.T) {
 	require.Nil(t, err)
 	require.Equal(t, dbtest.PostgresSchema(t, freshDB), dbtest.PostgresSchema(t, testDB))
 }
+
+func TestPostgresStore_MessagesCount_UsesPlannerEstimate(t *testing.T) {
+	// The manager calls MessagesCount every minute for a metric; a COUNT(*) scans the whole
+	// table on every call, so once the table has been analyzed, the planner's estimate is used
+	testDB := dbtest.CreateTestPostgres(t)
+	store, err := message.NewPostgresStore(testDB, 0, 0)
+	require.Nil(t, err)
+	for i := 0; i < 10; i++ {
+		require.Nil(t, store.AddMessage(model.NewDefaultMessage("mytopic", "some message")))
+	}
+
+	// Never analyzed: falls back to an exact count
+	count, err := store.MessagesCount()
+	require.Nil(t, err)
+	require.Equal(t, 10, count)
+
+	// Analyzed, then rows deleted: the estimate lags until the next (auto)analyze
+	_, err = testDB.Exec(`ANALYZE message`)
+	require.Nil(t, err)
+	_, err = testDB.Exec(`DELETE FROM message WHERE id IN (SELECT id FROM message LIMIT 4)`)
+	require.Nil(t, err)
+	count, err = store.MessagesCount()
+	require.Nil(t, err)
+	require.Equal(t, 10, count)
+}